1. Field of the Invention
The present invention relates to a flux cored wire, and more particularly to a flux cored wire for gas shielded arc welding, which is filled with a titania-based flux composition and employs carbon dioxide or a mixture of carbon dioxide and argon as a shield gas.
2. Description of the Related Art
In general, titania-based flux cored wires have been mainly applied to fabricate mild steels and high tensile strength steels having a tensile strength of 50 kgf/mm2 or more. Although the titania-based flux cored wires provide very excellent workability, there is a disadvantage in that upon low-temperature welding or high heat input welding, such conventional wires provide weld metals with poor impact toughness.
Indeed, the application of such titania-based flux cored wires has problems in ship fabrications, since the grade III of ship steel standards is strictly specified with respect to the impact values of metals(that is, more than 55 J at xe2x88x9220), and in steels for a low temperature use, such as aluminum killed steels (that is, more than 28 J at xe2x88x9240 to xe2x88x9250).
Meanwhile, using cored wires filled with a basic flux, such problems could be overcome. However, although weld metals have a satisfactory impact value at low temperature, some problems still remain, including that welding in all positions is unstable in terms of workability, and welding spatter and fume generation are increased.
Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a flux cored wire for gas shielded arc welding, which is capable of offering excellent workability and providing a weld metal with an improved impact value at low temperature.
In accordance with the present invention, the above and other objects can be accomplished by the provision of a flux cored wire for gas shielded arc welding, characterized in that a titania-based flux composition is filled into a sheath for mild steels of low-carbon steels, and the flux composition contains 4.0 to 8.0% TiO2, 1.0 to 3.0% Mn, 0.1 to 1.0% Si, 0.002 to 0.02% B, 0.2 to 0.45% Mg and 0.15 to 0.3% Al, by weight relative to the total weight 100% of the wire.
More preferably, the content ratio of Mg to Al may be 1.45 to 1.55.